I always use apple cider vinegar in my chicks water. When they first arrive I add sugar, too, to help them recover from the trip. I add 1 tbsp. per quart (1/4 cup per gallon), same amount of sugar. I realize that some people add less-1 tsp. per quart or even per gallon, but my amount seems to work for me. I use it because I use unmedicated feed, and it really seems to help keep them healthy and I have fewer pasty butts, even this time, when it has SNOWED for the last three days! (Getting to cold is one of the main reasons for pasting up.) And this after being in the high eighties the day before. Ah, spring weather...gotta love it!